The role of alkylhydroxybenzenes in the adaptation of Micrococcus luteus to heat shock

Abstract

The response of the gram-positive bacterium Micrococcus luteus to heat shock (45 degrees C, 15 min) and the adaptogenic activity of alkylhydroxybenzenes (AHB), which are extracellular growth-regulating substances of these bacteria, were studied. The perception of stress and the postshock behavior of M. luteus cells proved to depend on the growth phase and medium. The magnitude of stress response was more pronounced in cultures grown on synthetic medium than in cultures grown on rich medium (nutrient broth). During exponential or linear growth, the cells were more sensitive to the temperature effect than during decelerated growth. In linearly growing M. luteus cultures, the amount of total intra- and extracellular alkylhydroxybenzenes, the anabiosis inducers, increased in response to heat shock. AHB redistribution between cells and culture liquid occurred in the course of stress and after stress. In micrococci exposed to heat shock, an increase in the AHB concentration both in cells and culture liquid is likely a defense reaction of stress resistance. This conclusion was confirmed in the experiments with the addition 30 min before the heat shock of a chemical analogue of the anabiosis inducer, C7-AHB (12 mM), which protected M. luteus cells so that their intense growth was observed after shock without any lag. The protective effect of AHB is a result of their ability to form complexes with enzyme macromolecules and stabilize them. The data obtained extend the knowledge of the stress-protective functions of low-molecular-weight autoregulators and of the role of intercellular communications in the stress response of bacterial cultures.